Alien crayfish species are among the most successful of all invasive species. Even introductions of a few indivduals or escapes from garden ponds can result in newly established populations, which are notoriously difficult to controll or eradicate. For this reason, it has become illegal to pocess or breed a number of species under the EU legislation. Correct identification of crayfish is essential in the effords to controll the spread of these alien species.
The illustration shows two species, the Noble crayfish (right) and the White-clawed crasfish (middle), both of which are non-invasive native species in Slovenia. In grey (above left), an identification character is shown which helps to distinguish some American Swamp crayfish species, which are invasive.
These drawings are a part of a larger identification key to the now prohibited invasive crayfish species, which was commisioned by the Slovenian ministry of the environment and spatial planning.